A lane keeping assist apparatus is known in which an arrow in a direction against a departure direction, when a lane departure prevention control is operated, is displayed, and a size (including a length and a width) and a color of the arrow is changed according to a predominance degree of a driver on vehicle traveling. The higher the predominance degree of a driver becomes the less the intervention degree of a control, and thus the high predominance degree of a driver means a state in which a behavior of a vehicle depends on the operation of the driver.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2011-001049